This invention relates to a composition of matter useful as a dewatering aid in the processing of various mineral concentrates and coal. More particularly, this invention relates to such a composition comprising, in combination, a hydrophobic alcohol and a nonionic surfactant.
Valuable components of numerous minerals are concentrated by a variety of procedures that provide mineral concentrates that can then be further processed. One of the most widely used methods of concentration is froth flotation which is applicable to a wide variety of minerals including coal. After a mineral has been sufficiently enriched in valuable component by concentrating, it is usually subjected to dewatering so that it may be shipped more economically and/or further processed more readily. In dewatering, the mineral concentrate, in slurry form, is subjected to sedimentation, decantation, filtration or variations thereof to facilitate the removal of water therefrom. This removal of water decreases the weight of the concentrate and, in the case of coal, increases the BTU value per unit weight of concentrate; the removal of water by dewatering also reduces the energy requirements for subsequent evaporation of residual water when necessary, such as for smelting.
Sedimentation, in which the settling of suspended matter from the slurry is accomplished, is generally such an extremely slow process that it is generally the commercial practice to add a flocculating agent, such as glues, acids, starches, natural gums and the like, to cause the individual mineral particles to flocculate by interaction with the flocculating agent. Flocculation thus reduces the necessary holding time in settling basins or vessels before decantation of the supernatant liquor can be initiated.
Removal of the water from the resulting concentrated slurry is generally achieved through some form of filtration. The filter cake which forms during filtration is often substantially impermeable and filtration can be effected therethrough only at extremely slow rates and/or under extremely high pressures. Even when such an impermeable filter cake is not formed, it is advantageous to be able to accelerate the filtration speeds through the application of a dewatering aid which, when added in effective amounts to the concentrate slurry, reduces the residual water content thereof below that obtained in the absence of the additive, improves filter cake handling qualities and reduces binding of the filter medium. Surface active agents have long been known to be effective aids in the dewatering of mineral concentrates. Various flocculants have also been known to improve the filtration process. It was later found that the use of both a surface active agent and a flocculant led to advantages over either of the separate components alone at an equal total dosage.
In spite of the effectiveness of dewatering aids or combinations thereof, there nevertheless still exists the need for improved dewatering aids which provide lower residual water in the filtered concentrate and result in advantages thereby. Considering annual processing of many millions of tons of mineral ores and coal, such advantages could provide substantial savings in shipping costs and significant increases in available BTU values. The provision for improved dewatering aids, therefore, would fulfill a long-felt need and constitute a significant advance in the art.